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<h2 class="contents-heading">Table of Contents</h2>
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<div class="contents">
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<ul class="toc-numbered-mark">
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<li><a id="toc-General-Questions" href="#General-Questions">1 General Questions</a>
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<ul class="toc-numbered-mark">
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<li><a id="toc-Why-doesn_0027t-FFmpeg-support-feature-_005bxyz_005d_003f" href="#Why-doesn_0027t-FFmpeg-support-feature-_005bxyz_005d_003f">1.1 Why doesn’t FFmpeg support feature [xyz]?</a></li>
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<li><a id="toc-FFmpeg-does-not-support-codec-XXX_002e-Can-you-include-a-Windows-DLL-loader-to-support-it_003f" href="#FFmpeg-does-not-support-codec-XXX_002e-Can-you-include-a-Windows-DLL-loader-to-support-it_003f">1.2 FFmpeg does not support codec XXX. Can you include a Windows DLL loader to support it?</a></li>
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<li><a id="toc-I-cannot-read-this-file-although-this-format-seems-to-be-supported-by-ffmpeg_002e" href="#I-cannot-read-this-file-although-this-format-seems-to-be-supported-by-ffmpeg_002e">1.3 I cannot read this file although this format seems to be supported by ffmpeg.</a></li>
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<li><a id="toc-Which-codecs-are-supported-by-Windows_003f" href="#Which-codecs-are-supported-by-Windows_003f">1.4 Which codecs are supported by Windows?</a></li>
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</ul></li>
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<li><a id="toc-Compilation" href="#Compilation">2 Compilation</a>
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<ul class="toc-numbered-mark">
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<li><a id="toc-error_003a-can_0027t-find-a-register-in-class-_0027GENERAL_005fREGS_0027-while-reloading-_0027asm_0027" href="#error_003a-can_0027t-find-a-register-in-class-_0027GENERAL_005fREGS_0027-while-reloading-_0027asm_0027">2.1 <code class="code">error: can't find a register in class 'GENERAL_REGS' while reloading 'asm'</code></a></li>
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<li><a id="toc-I-have-installed-this-library-with-my-distro_0027s-package-manager_002e-Why-does-configure-not-see-it_003f" href="#I-have-installed-this-library-with-my-distro_0027s-package-manager_002e-Why-does-configure-not-see-it_003f">2.2 I have installed this library with my distro’s package manager. Why does <code class="command">configure</code> not see it?</a></li>
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<li><a id="toc-How-do-I-make-pkg_002dconfig-find-my-libraries_003f" href="#How-do-I-make-pkg_002dconfig-find-my-libraries_003f">2.3 How do I make <code class="command">pkg-config</code> find my libraries?</a></li>
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<li><a id="toc-How-do-I-use-pkg_002dconfig-when-cross_002dcompiling_003f" href="#How-do-I-use-pkg_002dconfig-when-cross_002dcompiling_003f">2.4 How do I use <code class="command">pkg-config</code> when cross-compiling?</a></li>
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</ul></li>
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<li><a id="toc-Usage" href="#Usage">3 Usage</a>
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<ul class="toc-numbered-mark">
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<li><a id="toc-ffmpeg-does-not-work_003b-what-is-wrong_003f" href="#ffmpeg-does-not-work_003b-what-is-wrong_003f">3.1 ffmpeg does not work; what is wrong?</a></li>
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<li><a id="toc-How-do-I-encode-single-pictures-into-movies_003f" href="#How-do-I-encode-single-pictures-into-movies_003f">3.2 How do I encode single pictures into movies?</a></li>
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<li><a id="toc-How-do-I-encode-movie-to-single-pictures_003f" href="#How-do-I-encode-movie-to-single-pictures_003f">3.3 How do I encode movie to single pictures?</a></li>
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<li><a id="toc-Why-do-I-see-a-slight-quality-degradation-with-multithreaded-MPEG_002a-encoding_003f" href="#Why-do-I-see-a-slight-quality-degradation-with-multithreaded-MPEG_002a-encoding_003f">3.4 Why do I see a slight quality degradation with multithreaded MPEG* encoding?</a></li>
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<li><a id="toc-How-can-I-read-from-the-standard-input-or-write-to-the-standard-output_003f" href="#How-can-I-read-from-the-standard-input-or-write-to-the-standard-output_003f">3.5 How can I read from the standard input or write to the standard output?</a></li>
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<li><a id="toc-_002df-jpeg-doesn_0027t-work_002e" href="#g_t_002df-jpeg-doesn_0027t-work_002e">3.6 -f jpeg doesn’t work.</a></li>
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<li><a id="toc-Why-can-I-not-change-the-frame-rate_003f" href="#Why-can-I-not-change-the-frame-rate_003f">3.7 Why can I not change the frame rate?</a></li>
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<li><a id="toc-How-do-I-encode-Xvid-or-DivX-video-with-ffmpeg_003f" href="#How-do-I-encode-Xvid-or-DivX-video-with-ffmpeg_003f">3.8 How do I encode Xvid or DivX video with ffmpeg?</a></li>
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<li><a id="toc-Which-are-good-parameters-for-encoding-high-quality-MPEG_002d4_003f" href="#Which-are-good-parameters-for-encoding-high-quality-MPEG_002d4_003f">3.9 Which are good parameters for encoding high quality MPEG-4?</a></li>
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<li><a id="toc-Which-are-good-parameters-for-encoding-high-quality-MPEG_002d1_002fMPEG_002d2_003f" href="#Which-are-good-parameters-for-encoding-high-quality-MPEG_002d1_002fMPEG_002d2_003f">3.10 Which are good parameters for encoding high quality MPEG-1/MPEG-2?</a></li>
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<li><a id="toc-Interlaced-video-looks-very-bad-when-encoded-with-ffmpeg_002c-what-is-wrong_003f" href="#Interlaced-video-looks-very-bad-when-encoded-with-ffmpeg_002c-what-is-wrong_003f">3.11 Interlaced video looks very bad when encoded with ffmpeg, what is wrong?</a></li>
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<li><a id="toc-How-can-I-read-DirectShow-files_003f" href="#How-can-I-read-DirectShow-files_003f">3.12 How can I read DirectShow files?</a></li>
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<li><a id="toc-How-can-I-join-video-files_003f" href="#How-can-I-join-video-files_003f">3.13 How can I join video files?</a></li>
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<li><a id="toc-How-can-I-concatenate-video-files_003f" href="#How-can-I-concatenate-video-files_003f">3.14 How can I concatenate video files?</a>
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<ul class="toc-numbered-mark">
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<li><a id="toc-Concatenating-using-the-concat-filter" href="#Concatenating-using-the-concat-filter">3.14.1 Concatenating using the concat <em class="emph">filter</em></a></li>
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<li><a id="toc-Concatenating-using-the-concat-demuxer" href="#Concatenating-using-the-concat-demuxer">3.14.2 Concatenating using the concat <em class="emph">demuxer</em></a></li>
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<li><a id="toc-Concatenating-using-the-concat-protocol-_0028file-level_0029" href="#Concatenating-using-the-concat-protocol-_0028file-level_0029">3.14.3 Concatenating using the concat <em class="emph">protocol</em> (file level)</a></li>
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<li><a id="toc-Concatenating-using-raw-audio-and-video" href="#Concatenating-using-raw-audio-and-video">3.14.4 Concatenating using raw audio and video</a></li>
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</ul></li>
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<li><a id="toc-Using-_002df-lavfi_002c-audio-becomes-mono-for-no-apparent-reason_002e" href="#Using-_002df-lavfi_002c-audio-becomes-mono-for-no-apparent-reason_002e">3.15 Using <samp class="option">-f lavfi</samp>, audio becomes mono for no apparent reason.</a></li>
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<li><a id="toc-Why-does-FFmpeg-not-see-the-subtitles-in-my-VOB-file_003f" href="#Why-does-FFmpeg-not-see-the-subtitles-in-my-VOB-file_003f">3.16 Why does FFmpeg not see the subtitles in my VOB file?</a></li>
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<li><a id="toc-Why-was-the-ffmpeg-_002dsameq-option-removed_003f-What-to-use-instead_003f" href="#Why-was-the-ffmpeg-_002dsameq-option-removed_003f-What-to-use-instead_003f">3.17 Why was the <code class="command">ffmpeg</code> <samp class="option">-sameq</samp> option removed? What to use instead?</a></li>
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<li><a id="toc-I-have-a-stretched-video_002c-why-does-scaling-does-not-fix-it_003f" href="#I-have-a-stretched-video_002c-why-does-scaling-does-not-fix-it_003f">3.18 I have a stretched video, why does scaling does not fix it?</a></li>
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<li><a id="toc-How-do-I-run-ffmpeg-as-a-background-task_003f" href="#How-do-I-run-ffmpeg-as-a-background-task_003f">3.19 How do I run ffmpeg as a background task?</a></li>
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<li><a id="toc-How-do-I-prevent-ffmpeg-from-suspending-with-a-message-like-suspended-_0028tty-output_0029_003f" href="#How-do-I-prevent-ffmpeg-from-suspending-with-a-message-like-suspended-_0028tty-output_0029_003f">3.20 How do I prevent ffmpeg from suspending with a message like <em class="emph">suspended (tty output)</em>?</a></li>
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</ul></li>
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<li><a id="toc-Development" href="#Development">4 Development</a>
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<ul class="toc-numbered-mark">
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<li><a id="toc-Are-there-examples-illustrating-how-to-use-the-FFmpeg-libraries_002c-particularly-libavcodec-and-libavformat_003f" href="#Are-there-examples-illustrating-how-to-use-the-FFmpeg-libraries_002c-particularly-libavcodec-and-libavformat_003f">4.1 Are there examples illustrating how to use the FFmpeg libraries, particularly libavcodec and libavformat?</a></li>
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<li><a id="toc-Can-you-support-my-C-compiler-XXX_003f" href="#Can-you-support-my-C-compiler-XXX_003f">4.2 Can you support my C compiler XXX?</a></li>
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<li><a id="toc-Is-Microsoft-Visual-C_002b_002b-supported_003f" href="#Is-Microsoft-Visual-C_002b_002b-supported_003f">4.3 Is Microsoft Visual C++ supported?</a></li>
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<li><a id="toc-Can-you-add-automake_002c-libtool-or-autoconf-support_003f" href="#Can-you-add-automake_002c-libtool-or-autoconf-support_003f">4.4 Can you add automake, libtool or autoconf support?</a></li>
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<li><a id="toc-Why-not-rewrite-FFmpeg-in-object_002doriented-C_002b_002b_003f" href="#Why-not-rewrite-FFmpeg-in-object_002doriented-C_002b_002b_003f">4.5 Why not rewrite FFmpeg in object-oriented C++?</a></li>
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<li><a id="toc-Why-are-the-ffmpeg-programs-devoid-of-debugging-symbols_003f" href="#Why-are-the-ffmpeg-programs-devoid-of-debugging-symbols_003f">4.6 Why are the ffmpeg programs devoid of debugging symbols?</a></li>
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<li><a id="toc-I-do-not-like-the-LGPL_002c-can-I-contribute-code-under-the-GPL-instead_003f" href="#I-do-not-like-the-LGPL_002c-can-I-contribute-code-under-the-GPL-instead_003f">4.7 I do not like the LGPL, can I contribute code under the GPL instead?</a></li>
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<li><a id="toc-I_0027m-using-FFmpeg-from-within-my-C-application-but-the-linker-complains-about-missing-symbols-from-the-libraries-themselves_002e" href="#I_0027m-using-FFmpeg-from-within-my-C-application-but-the-linker-complains-about-missing-symbols-from-the-libraries-themselves_002e">4.8 I’m using FFmpeg from within my C application but the linker complains about missing symbols from the libraries themselves.</a></li>
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<li><a id="toc-I_0027m-using-FFmpeg-from-within-my-C_002b_002b-application-but-the-linker-complains-about-missing-symbols-which-seem-to-be-available_002e" href="#I_0027m-using-FFmpeg-from-within-my-C_002b_002b-application-but-the-linker-complains-about-missing-symbols-which-seem-to-be-available_002e">4.9 I’m using FFmpeg from within my C++ application but the linker complains about missing symbols which seem to be available.</a></li>
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<li><a id="toc-I_0027m-using-libavutil-from-within-my-C_002b_002b-application-but-the-compiler-complains-about-_0027UINT64_005fC_0027-was-not-declared-in-this-scope" href="#I_0027m-using-libavutil-from-within-my-C_002b_002b-application-but-the-compiler-complains-about-_0027UINT64_005fC_0027-was-not-declared-in-this-scope">4.10 I’m using libavutil from within my C++ application but the compiler complains about ’UINT64_C’ was not declared in this scope</a></li>
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||
<li><a id="toc-I-have-a-file-in-memory-_002f-a-API-different-from-_002aopen_002f_002aread_002f-libc-how-do-I-use-it-with-libavformat_003f" href="#I-have-a-file-in-memory-_002f-a-API-different-from-_002aopen_002f_002aread_002f-libc-how-do-I-use-it-with-libavformat_003f">4.11 I have a file in memory / a API different from *open/*read/ libc how do I use it with libavformat?</a></li>
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<li><a id="toc-Where-is-the-documentation-about-ffv1_002c-msmpeg4_002c-asv1_002c-4xm_003f" href="#Where-is-the-documentation-about-ffv1_002c-msmpeg4_002c-asv1_002c-4xm_003f">4.12 Where is the documentation about ffv1, msmpeg4, asv1, 4xm?</a></li>
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<li><a id="toc-How-do-I-feed-H_002e263_002dRTP-_0028and-other-codecs-in-RTP_0029-to-libavcodec_003f" href="#How-do-I-feed-H_002e263_002dRTP-_0028and-other-codecs-in-RTP_0029-to-libavcodec_003f">4.13 How do I feed H.263-RTP (and other codecs in RTP) to libavcodec?</a></li>
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<li><a id="toc-AVStream_002er_005fframe_005frate-is-wrong_002c-it-is-much-larger-than-the-frame-rate_002e" href="#AVStream_002er_005fframe_005frate-is-wrong_002c-it-is-much-larger-than-the-frame-rate_002e">4.14 AVStream.r_frame_rate is wrong, it is much larger than the frame rate.</a></li>
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<li><a id="toc-Why-is-make-fate-not-running-all-tests_003f" href="#Why-is-make-fate-not-running-all-tests_003f">4.15 Why is <code class="code">make fate</code> not running all tests?</a></li>
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<li><a id="toc-Why-is-make-fate-not-finding-the-samples_003f" href="#Why-is-make-fate-not-finding-the-samples_003f">4.16 Why is <code class="code">make fate</code> not finding the samples?</a></li>
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</ul></li>
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</ul>
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</div>
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</div>
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<div class="chapter-level-extent" id="General-Questions">
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<h2 class="chapter">1 General Questions</h2>
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<ul class="mini-toc">
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<li><a href="#Why-doesn_0027t-FFmpeg-support-feature-_005bxyz_005d_003f" accesskey="1">Why doesn’t FFmpeg support feature [xyz]?</a></li>
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<li><a href="#FFmpeg-does-not-support-codec-XXX_002e-Can-you-include-a-Windows-DLL-loader-to-support-it_003f" accesskey="2">FFmpeg does not support codec XXX. Can you include a Windows DLL loader to support it?</a></li>
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<li><a href="#I-cannot-read-this-file-although-this-format-seems-to-be-supported-by-ffmpeg_002e" accesskey="3">I cannot read this file although this format seems to be supported by ffmpeg.</a></li>
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<li><a href="#Which-codecs-are-supported-by-Windows_003f" accesskey="4">Which codecs are supported by Windows?</a></li>
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</ul>
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<div class="section-level-extent" id="Why-doesn_0027t-FFmpeg-support-feature-_005bxyz_005d_003f">
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<h3 class="section">1.1 Why doesn’t FFmpeg support feature [xyz]?</h3>
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<p>Because no one has taken on that task yet. FFmpeg development is
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driven by the tasks that are important to the individual developers.
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If there is a feature that is important to you, the best way to get
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it implemented is to undertake the task yourself or sponsor a developer.
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</p>
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</div>
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<div class="section-level-extent" id="FFmpeg-does-not-support-codec-XXX_002e-Can-you-include-a-Windows-DLL-loader-to-support-it_003f">
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<h3 class="section">1.2 FFmpeg does not support codec XXX. Can you include a Windows DLL loader to support it?</h3>
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<p>No. Windows DLLs are not portable, bloated and often slow.
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Moreover FFmpeg strives to support all codecs natively.
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A DLL loader is not conducive to that goal.
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</p>
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</div>
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||
<div class="section-level-extent" id="I-cannot-read-this-file-although-this-format-seems-to-be-supported-by-ffmpeg_002e">
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||
<h3 class="section">1.3 I cannot read this file although this format seems to be supported by ffmpeg.</h3>
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<p>Even if ffmpeg can read the container format, it may not support all its
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codecs. Please consult the supported codec list in the ffmpeg
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documentation.
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||
</p>
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||
</div>
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||
<div class="section-level-extent" id="Which-codecs-are-supported-by-Windows_003f">
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||
<h3 class="section">1.4 Which codecs are supported by Windows?</h3>
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<p>Windows does not support standard formats like MPEG very well, unless you
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install some additional codecs.
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</p>
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<p>The following list of video codecs should work on most Windows systems:
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||
</p><dl class="table">
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||
<dt><samp class="option">msmpeg4v2</samp></dt>
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<dd><p>.avi/.asf
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</p></dd>
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<dt><samp class="option">msmpeg4</samp></dt>
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<dd><p>.asf only
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</p></dd>
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<dt><samp class="option">wmv1</samp></dt>
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||
<dd><p>.asf only
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</p></dd>
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||
<dt><samp class="option">wmv2</samp></dt>
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||
<dd><p>.asf only
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</p></dd>
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<dt><samp class="option">mpeg4</samp></dt>
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<dd><p>Only if you have some MPEG-4 codec like ffdshow or Xvid installed.
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</p></dd>
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||
<dt><samp class="option">mpeg1video</samp></dt>
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||
<dd><p>.mpg only
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</p></dd>
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||
</dl>
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||
<p>Note, ASF files often have .wmv or .wma extensions in Windows. It should also
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be mentioned that Microsoft claims a patent on the ASF format, and may sue
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or threaten users who create ASF files with non-Microsoft software. It is
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strongly advised to avoid ASF where possible.
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||
</p>
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<p>The following list of audio codecs should work on most Windows systems:
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</p><dl class="table">
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<dt><samp class="option">adpcm_ima_wav</samp></dt>
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||
<dt><samp class="option">adpcm_ms</samp></dt>
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<dt><samp class="option">pcm_s16le</samp></dt>
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<dd><p>always
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</p></dd>
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<dt><samp class="option">libmp3lame</samp></dt>
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<dd><p>If some MP3 codec like LAME is installed.
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</p></dd>
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||
</dl>
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||
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||
</div>
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||
</div>
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<div class="chapter-level-extent" id="Compilation">
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<h2 class="chapter">2 Compilation</h2>
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||
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||
<ul class="mini-toc">
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||
<li><a href="#error_003a-can_0027t-find-a-register-in-class-_0027GENERAL_005fREGS_0027-while-reloading-_0027asm_0027" accesskey="1"><code class="code">error: can't find a register in class 'GENERAL_REGS' while reloading 'asm'</code></a></li>
|
||
<li><a href="#I-have-installed-this-library-with-my-distro_0027s-package-manager_002e-Why-does-configure-not-see-it_003f" accesskey="2">I have installed this library with my distro’s package manager. Why does <code class="command">configure</code> not see it?</a></li>
|
||
<li><a href="#How-do-I-make-pkg_002dconfig-find-my-libraries_003f" accesskey="3">How do I make <code class="command">pkg-config</code> find my libraries?</a></li>
|
||
<li><a href="#How-do-I-use-pkg_002dconfig-when-cross_002dcompiling_003f" accesskey="4">How do I use <code class="command">pkg-config</code> when cross-compiling?</a></li>
|
||
</ul>
|
||
<div class="section-level-extent" id="error_003a-can_0027t-find-a-register-in-class-_0027GENERAL_005fREGS_0027-while-reloading-_0027asm_0027">
|
||
<h3 class="section">2.1 <code class="code">error: can't find a register in class 'GENERAL_REGS' while reloading 'asm'</code></h3>
|
||
|
||
<p>This is a bug in gcc. Do not report it to us. Instead, please report it to
|
||
the gcc developers. Note that we will not add workarounds for gcc bugs.
|
||
</p>
|
||
<p>Also note that (some of) the gcc developers believe this is not a bug or
|
||
not a bug they should fix:
|
||
<a class="url" href="https://gcc.gnu.org/bugzilla/show_bug.cgi?id=11203">https://gcc.gnu.org/bugzilla/show_bug.cgi?id=11203</a>.
|
||
Then again, some of them do not know the difference between an undecidable
|
||
problem and an NP-hard problem...
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="I-have-installed-this-library-with-my-distro_0027s-package-manager_002e-Why-does-configure-not-see-it_003f">
|
||
<h3 class="section">2.2 I have installed this library with my distro’s package manager. Why does <code class="command">configure</code> not see it?</h3>
|
||
|
||
<p>Distributions usually split libraries in several packages. The main package
|
||
contains the files necessary to run programs using the library. The
|
||
development package contains the files necessary to build programs using the
|
||
library. Sometimes, docs and/or data are in a separate package too.
|
||
</p>
|
||
<p>To build FFmpeg, you need to install the development package. It is usually
|
||
called <samp class="file">libfoo-dev</samp> or <samp class="file">libfoo-devel</samp>. You can remove it after the
|
||
build is finished, but be sure to keep the main package.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="How-do-I-make-pkg_002dconfig-find-my-libraries_003f">
|
||
<h3 class="section">2.3 How do I make <code class="command">pkg-config</code> find my libraries?</h3>
|
||
|
||
<p>Somewhere along with your libraries, there is a <samp class="file">.pc</samp> file (or several)
|
||
in a <samp class="file">pkgconfig</samp> directory. You need to set environment variables to
|
||
point <code class="command">pkg-config</code> to these files.
|
||
</p>
|
||
<p>If you need to <em class="emph">add</em> directories to <code class="command">pkg-config</code>’s search list
|
||
(typical use case: library installed separately), add it to
|
||
<code class="code">$PKG_CONFIG_PATH</code>:
|
||
</p>
|
||
<div class="example">
|
||
<pre class="example-preformatted">export PKG_CONFIG_PATH=/opt/x264/lib/pkgconfig:/opt/opus/lib/pkgconfig
|
||
</pre></div>
|
||
|
||
<p>If you need to <em class="emph">replace</em> <code class="command">pkg-config</code>’s search list
|
||
(typical use case: cross-compiling), set it in
|
||
<code class="code">$PKG_CONFIG_LIBDIR</code>:
|
||
</p>
|
||
<div class="example">
|
||
<pre class="example-preformatted">export PKG_CONFIG_LIBDIR=/home/me/cross/usr/lib/pkgconfig:/home/me/cross/usr/local/lib/pkgconfig
|
||
</pre></div>
|
||
|
||
<p>If you need to know the library’s internal dependencies (typical use: static
|
||
linking), add the <code class="code">--static</code> option to <code class="command">pkg-config</code>:
|
||
</p>
|
||
<div class="example">
|
||
<pre class="example-preformatted">./configure --pkg-config-flags=--static
|
||
</pre></div>
|
||
|
||
</div>
|
||
<div class="section-level-extent" id="How-do-I-use-pkg_002dconfig-when-cross_002dcompiling_003f">
|
||
<h3 class="section">2.4 How do I use <code class="command">pkg-config</code> when cross-compiling?</h3>
|
||
|
||
<p>The best way is to install <code class="command">pkg-config</code> in your cross-compilation
|
||
environment. It will automatically use the cross-compilation libraries.
|
||
</p>
|
||
<p>You can also use <code class="command">pkg-config</code> from the host environment by
|
||
specifying explicitly <code class="code">--pkg-config=pkg-config</code> to <code class="command">configure</code>.
|
||
In that case, you must point <code class="command">pkg-config</code> to the correct directories
|
||
using the <code class="code">PKG_CONFIG_LIBDIR</code>, as explained in the previous entry.
|
||
</p>
|
||
<p>As an intermediate solution, you can place in your cross-compilation
|
||
environment a script that calls the host <code class="command">pkg-config</code> with
|
||
<code class="code">PKG_CONFIG_LIBDIR</code> set. That script can look like that:
|
||
</p>
|
||
<div class="example">
|
||
<pre class="example-preformatted">#!/bin/sh
|
||
PKG_CONFIG_LIBDIR=/path/to/cross/lib/pkgconfig
|
||
export PKG_CONFIG_LIBDIR
|
||
exec /usr/bin/pkg-config "$@"
|
||
</pre></div>
|
||
|
||
</div>
|
||
</div>
|
||
<div class="chapter-level-extent" id="Usage">
|
||
<h2 class="chapter">3 Usage</h2>
|
||
|
||
<ul class="mini-toc">
|
||
<li><a href="#ffmpeg-does-not-work_003b-what-is-wrong_003f" accesskey="1">ffmpeg does not work; what is wrong?</a></li>
|
||
<li><a href="#How-do-I-encode-single-pictures-into-movies_003f" accesskey="2">How do I encode single pictures into movies?</a></li>
|
||
<li><a href="#How-do-I-encode-movie-to-single-pictures_003f" accesskey="3">How do I encode movie to single pictures?</a></li>
|
||
<li><a href="#Why-do-I-see-a-slight-quality-degradation-with-multithreaded-MPEG_002a-encoding_003f" accesskey="4">Why do I see a slight quality degradation with multithreaded MPEG* encoding?</a></li>
|
||
<li><a href="#How-can-I-read-from-the-standard-input-or-write-to-the-standard-output_003f" accesskey="5">How can I read from the standard input or write to the standard output?</a></li>
|
||
<li><a href="#g_t_002df-jpeg-doesn_0027t-work_002e" accesskey="6">-f jpeg doesn’t work.</a></li>
|
||
<li><a href="#Why-can-I-not-change-the-frame-rate_003f" accesskey="7">Why can I not change the frame rate?</a></li>
|
||
<li><a href="#How-do-I-encode-Xvid-or-DivX-video-with-ffmpeg_003f" accesskey="8">How do I encode Xvid or DivX video with ffmpeg?</a></li>
|
||
<li><a href="#Which-are-good-parameters-for-encoding-high-quality-MPEG_002d4_003f" accesskey="9">Which are good parameters for encoding high quality MPEG-4?</a></li>
|
||
<li><a href="#Which-are-good-parameters-for-encoding-high-quality-MPEG_002d1_002fMPEG_002d2_003f">Which are good parameters for encoding high quality MPEG-1/MPEG-2?</a></li>
|
||
<li><a href="#Interlaced-video-looks-very-bad-when-encoded-with-ffmpeg_002c-what-is-wrong_003f">Interlaced video looks very bad when encoded with ffmpeg, what is wrong?</a></li>
|
||
<li><a href="#How-can-I-read-DirectShow-files_003f">How can I read DirectShow files?</a></li>
|
||
<li><a href="#How-can-I-join-video-files_003f">How can I join video files?</a></li>
|
||
<li><a href="#How-can-I-concatenate-video-files_003f">How can I concatenate video files?</a></li>
|
||
<li><a href="#Using-_002df-lavfi_002c-audio-becomes-mono-for-no-apparent-reason_002e">Using <samp class="option">-f lavfi</samp>, audio becomes mono for no apparent reason.</a></li>
|
||
<li><a href="#Why-does-FFmpeg-not-see-the-subtitles-in-my-VOB-file_003f">Why does FFmpeg not see the subtitles in my VOB file?</a></li>
|
||
<li><a href="#Why-was-the-ffmpeg-_002dsameq-option-removed_003f-What-to-use-instead_003f">Why was the <code class="command">ffmpeg</code> <samp class="option">-sameq</samp> option removed? What to use instead?</a></li>
|
||
<li><a href="#I-have-a-stretched-video_002c-why-does-scaling-does-not-fix-it_003f">I have a stretched video, why does scaling does not fix it?</a></li>
|
||
<li><a href="#How-do-I-run-ffmpeg-as-a-background-task_003f">How do I run ffmpeg as a background task?</a></li>
|
||
<li><a href="#How-do-I-prevent-ffmpeg-from-suspending-with-a-message-like-suspended-_0028tty-output_0029_003f">How do I prevent ffmpeg from suspending with a message like <em class="emph">suspended (tty output)</em>?</a></li>
|
||
</ul>
|
||
<div class="section-level-extent" id="ffmpeg-does-not-work_003b-what-is-wrong_003f">
|
||
<h3 class="section">3.1 ffmpeg does not work; what is wrong?</h3>
|
||
|
||
<p>Try a <code class="code">make distclean</code> in the ffmpeg source directory before the build.
|
||
If this does not help see
|
||
(<a class="url" href="https://ffmpeg.org/bugreports.html">https://ffmpeg.org/bugreports.html</a>).
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="How-do-I-encode-single-pictures-into-movies_003f">
|
||
<h3 class="section">3.2 How do I encode single pictures into movies?</h3>
|
||
|
||
<p>First, rename your pictures to follow a numerical sequence.
|
||
For example, img1.jpg, img2.jpg, img3.jpg,...
|
||
Then you may run:
|
||
</p>
|
||
<div class="example">
|
||
<pre class="example-preformatted">ffmpeg -f image2 -i img%d.jpg /tmp/a.mpg
|
||
</pre></div>
|
||
|
||
<p>Notice that ‘<samp class="samp">%d</samp>’ is replaced by the image number.
|
||
</p>
|
||
<p><samp class="file">img%03d.jpg</samp> means the sequence <samp class="file">img001.jpg</samp>, <samp class="file">img002.jpg</samp>, etc.
|
||
</p>
|
||
<p>Use the <samp class="option">-start_number</samp> option to declare a starting number for
|
||
the sequence. This is useful if your sequence does not start with
|
||
<samp class="file">img001.jpg</samp> but is still in a numerical order. The following
|
||
example will start with <samp class="file">img100.jpg</samp>:
|
||
</p>
|
||
<div class="example">
|
||
<pre class="example-preformatted">ffmpeg -f image2 -start_number 100 -i img%d.jpg /tmp/a.mpg
|
||
</pre></div>
|
||
|
||
<p>If you have large number of pictures to rename, you can use the
|
||
following command to ease the burden. The command, using the bourne
|
||
shell syntax, symbolically links all files in the current directory
|
||
that match <code class="code">*jpg</code> to the <samp class="file">/tmp</samp> directory in the sequence of
|
||
<samp class="file">img001.jpg</samp>, <samp class="file">img002.jpg</samp> and so on.
|
||
</p>
|
||
<div class="example">
|
||
<pre class="example-preformatted">x=1; for i in *jpg; do counter=$(printf %03d $x); ln -s "$i" /tmp/img"$counter".jpg; x=$(($x+1)); done
|
||
</pre></div>
|
||
|
||
<p>If you want to sequence them by oldest modified first, substitute
|
||
<code class="code">$(ls -r -t *jpg)</code> in place of <code class="code">*jpg</code>.
|
||
</p>
|
||
<p>Then run:
|
||
</p>
|
||
<div class="example">
|
||
<pre class="example-preformatted">ffmpeg -f image2 -i /tmp/img%03d.jpg /tmp/a.mpg
|
||
</pre></div>
|
||
|
||
<p>The same logic is used for any image format that ffmpeg reads.
|
||
</p>
|
||
<p>You can also use <code class="command">cat</code> to pipe images to ffmpeg:
|
||
</p>
|
||
<div class="example">
|
||
<pre class="example-preformatted">cat *.jpg | ffmpeg -f image2pipe -c:v mjpeg -i - output.mpg
|
||
</pre></div>
|
||
|
||
</div>
|
||
<div class="section-level-extent" id="How-do-I-encode-movie-to-single-pictures_003f">
|
||
<h3 class="section">3.3 How do I encode movie to single pictures?</h3>
|
||
|
||
<p>Use:
|
||
</p>
|
||
<div class="example">
|
||
<pre class="example-preformatted">ffmpeg -i movie.mpg movie%d.jpg
|
||
</pre></div>
|
||
|
||
<p>The <samp class="file">movie.mpg</samp> used as input will be converted to
|
||
<samp class="file">movie1.jpg</samp>, <samp class="file">movie2.jpg</samp>, etc...
|
||
</p>
|
||
<p>Instead of relying on file format self-recognition, you may also use
|
||
</p><dl class="table">
|
||
<dt><samp class="option">-c:v ppm</samp></dt>
|
||
<dt><samp class="option">-c:v png</samp></dt>
|
||
<dt><samp class="option">-c:v mjpeg</samp></dt>
|
||
</dl>
|
||
<p>to force the encoding.
|
||
</p>
|
||
<p>Applying that to the previous example:
|
||
</p><div class="example">
|
||
<pre class="example-preformatted">ffmpeg -i movie.mpg -f image2 -c:v mjpeg menu%d.jpg
|
||
</pre></div>
|
||
|
||
<p>Beware that there is no "jpeg" codec. Use "mjpeg" instead.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="Why-do-I-see-a-slight-quality-degradation-with-multithreaded-MPEG_002a-encoding_003f">
|
||
<h3 class="section">3.4 Why do I see a slight quality degradation with multithreaded MPEG* encoding?</h3>
|
||
|
||
<p>For multithreaded MPEG* encoding, the encoded slices must be independent,
|
||
otherwise thread n would practically have to wait for n-1 to finish, so it’s
|
||
quite logical that there is a small reduction of quality. This is not a bug.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="How-can-I-read-from-the-standard-input-or-write-to-the-standard-output_003f">
|
||
<h3 class="section">3.5 How can I read from the standard input or write to the standard output?</h3>
|
||
|
||
<p>Use <samp class="file">-</samp> as file name.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="g_t_002df-jpeg-doesn_0027t-work_002e">
|
||
<h3 class="section">3.6 -f jpeg doesn’t work.</h3>
|
||
|
||
<p>Try ’-f image2 test%d.jpg’.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="Why-can-I-not-change-the-frame-rate_003f">
|
||
<h3 class="section">3.7 Why can I not change the frame rate?</h3>
|
||
|
||
<p>Some codecs, like MPEG-1/2, only allow a small number of fixed frame rates.
|
||
Choose a different codec with the -c:v command line option.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="How-do-I-encode-Xvid-or-DivX-video-with-ffmpeg_003f">
|
||
<h3 class="section">3.8 How do I encode Xvid or DivX video with ffmpeg?</h3>
|
||
|
||
<p>Both Xvid and DivX (version 4+) are implementations of the ISO MPEG-4
|
||
standard (note that there are many other coding formats that use this
|
||
same standard). Thus, use ’-c:v mpeg4’ to encode in these formats. The
|
||
default fourcc stored in an MPEG-4-coded file will be ’FMP4’. If you want
|
||
a different fourcc, use the ’-vtag’ option. E.g., ’-vtag xvid’ will
|
||
force the fourcc ’xvid’ to be stored as the video fourcc rather than the
|
||
default.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="Which-are-good-parameters-for-encoding-high-quality-MPEG_002d4_003f">
|
||
<h3 class="section">3.9 Which are good parameters for encoding high quality MPEG-4?</h3>
|
||
|
||
<p>’-mbd rd -flags +mv4+aic -trellis 2 -cmp 2 -subcmp 2 -g 300 -pass 1/2’,
|
||
things to try: ’-bf 2’, ’-mpv_flags qp_rd’, ’-mpv_flags mv0’, ’-mpv_flags skip_rd’.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="Which-are-good-parameters-for-encoding-high-quality-MPEG_002d1_002fMPEG_002d2_003f">
|
||
<h3 class="section">3.10 Which are good parameters for encoding high quality MPEG-1/MPEG-2?</h3>
|
||
|
||
<p>’-mbd rd -trellis 2 -cmp 2 -subcmp 2 -g 100 -pass 1/2’
|
||
but beware the ’-g 100’ might cause problems with some decoders.
|
||
Things to try: ’-bf 2’, ’-mpv_flags qp_rd’, ’-mpv_flags mv0’, ’-mpv_flags skip_rd’.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="Interlaced-video-looks-very-bad-when-encoded-with-ffmpeg_002c-what-is-wrong_003f">
|
||
<h3 class="section">3.11 Interlaced video looks very bad when encoded with ffmpeg, what is wrong?</h3>
|
||
|
||
<p>You should use ’-flags +ilme+ildct’ and maybe ’-flags +alt’ for interlaced
|
||
material, and try ’-top 0/1’ if the result looks really messed-up.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="How-can-I-read-DirectShow-files_003f">
|
||
<h3 class="section">3.12 How can I read DirectShow files?</h3>
|
||
|
||
<p>If you have built FFmpeg with <code class="code">./configure --enable-avisynth</code>
|
||
(only possible on MinGW/Cygwin platforms),
|
||
then you may use any file that DirectShow can read as input.
|
||
</p>
|
||
<p>Just create an "input.avs" text file with this single line ...
|
||
</p><div class="example">
|
||
<pre class="example-preformatted">DirectShowSource("C:\path to your file\yourfile.asf")
|
||
</pre></div>
|
||
<p>... and then feed that text file to ffmpeg:
|
||
</p><div class="example">
|
||
<pre class="example-preformatted">ffmpeg -i input.avs
|
||
</pre></div>
|
||
|
||
<p>For ANY other help on AviSynth, please visit the
|
||
<a class="uref" href="http://www.avisynth.org/">AviSynth homepage</a>.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="How-can-I-join-video-files_003f">
|
||
<h3 class="section">3.13 How can I join video files?</h3>
|
||
|
||
<p>To "join" video files is quite ambiguous. The following list explains the
|
||
different kinds of "joining" and points out how those are addressed in
|
||
FFmpeg. To join video files may mean:
|
||
</p>
|
||
<ul class="itemize mark-bullet">
|
||
<li>To put them one after the other: this is called to <em class="emph">concatenate</em> them
|
||
(in short: concat) and is addressed
|
||
<a class="ref" href="#How-can-I-concatenate-video-files">in this very faq</a>.
|
||
|
||
</li><li>To put them together in the same file, to let the user choose between the
|
||
different versions (example: different audio languages): this is called to
|
||
<em class="emph">multiplex</em> them together (in short: mux), and is done by simply
|
||
invoking ffmpeg with several <samp class="option">-i</samp> options.
|
||
|
||
</li><li>For audio, to put all channels together in a single stream (example: two
|
||
mono streams into one stereo stream): this is sometimes called to
|
||
<em class="emph">merge</em> them, and can be done using the
|
||
<a class="url" href="ffmpeg-filters.html#amerge"><code class="code">amerge</code></a> filter.
|
||
|
||
</li><li>For audio, to play one on top of the other: this is called to <em class="emph">mix</em>
|
||
them, and can be done by first merging them into a single stream and then
|
||
using the <a class="url" href="ffmpeg-filters.html#pan"><code class="code">pan</code></a> filter to mix
|
||
the channels at will.
|
||
|
||
</li><li>For video, to display both together, side by side or one on top of a part of
|
||
the other; it can be done using the
|
||
<a class="url" href="ffmpeg-filters.html#overlay"><code class="code">overlay</code></a> video filter.
|
||
|
||
</li></ul>
|
||
|
||
<a class="anchor" id="How-can-I-concatenate-video-files"></a></div>
|
||
<div class="section-level-extent" id="How-can-I-concatenate-video-files_003f">
|
||
<h3 class="section">3.14 How can I concatenate video files?</h3>
|
||
|
||
<p>There are several solutions, depending on the exact circumstances.
|
||
</p>
|
||
<ul class="mini-toc">
|
||
<li><a href="#Concatenating-using-the-concat-filter" accesskey="1">Concatenating using the concat <em class="emph">filter</em></a></li>
|
||
<li><a href="#Concatenating-using-the-concat-demuxer" accesskey="2">Concatenating using the concat <em class="emph">demuxer</em></a></li>
|
||
<li><a href="#Concatenating-using-the-concat-protocol-_0028file-level_0029" accesskey="3">Concatenating using the concat <em class="emph">protocol</em> (file level)</a></li>
|
||
<li><a href="#Concatenating-using-raw-audio-and-video" accesskey="4">Concatenating using raw audio and video</a></li>
|
||
</ul>
|
||
<div class="subsection-level-extent" id="Concatenating-using-the-concat-filter">
|
||
<h4 class="subsection">3.14.1 Concatenating using the concat <em class="emph">filter</em></h4>
|
||
|
||
<p>FFmpeg has a <a class="url" href="ffmpeg-filters.html#concat"><code class="code">concat</code></a> filter designed specifically for that, with examples in the
|
||
documentation. This operation is recommended if you need to re-encode.
|
||
</p>
|
||
</div>
|
||
<div class="subsection-level-extent" id="Concatenating-using-the-concat-demuxer">
|
||
<h4 class="subsection">3.14.2 Concatenating using the concat <em class="emph">demuxer</em></h4>
|
||
|
||
<p>FFmpeg has a <a class="url" href="ffmpeg-formats.html#concat"><code class="code">concat</code></a> demuxer which you can use when you want to avoid a re-encode and
|
||
your format doesn’t support file level concatenation.
|
||
</p>
|
||
</div>
|
||
<div class="subsection-level-extent" id="Concatenating-using-the-concat-protocol-_0028file-level_0029">
|
||
<h4 class="subsection">3.14.3 Concatenating using the concat <em class="emph">protocol</em> (file level)</h4>
|
||
|
||
<p>FFmpeg has a <a class="url" href="ffmpeg-protocols.html#concat"><code class="code">concat</code></a> protocol designed specifically for that, with examples in the
|
||
documentation.
|
||
</p>
|
||
<p>A few multimedia containers (MPEG-1, MPEG-2 PS, DV) allow one to concatenate
|
||
video by merely concatenating the files containing them.
|
||
</p>
|
||
<p>Hence you may concatenate your multimedia files by first transcoding them to
|
||
these privileged formats, then using the humble <code class="code">cat</code> command (or the
|
||
equally humble <code class="code">copy</code> under Windows), and finally transcoding back to your
|
||
format of choice.
|
||
</p>
|
||
<div class="example">
|
||
<pre class="example-preformatted">ffmpeg -i input1.avi -qscale:v 1 intermediate1.mpg
|
||
ffmpeg -i input2.avi -qscale:v 1 intermediate2.mpg
|
||
cat intermediate1.mpg intermediate2.mpg > intermediate_all.mpg
|
||
ffmpeg -i intermediate_all.mpg -qscale:v 2 output.avi
|
||
</pre></div>
|
||
|
||
<p>Additionally, you can use the <code class="code">concat</code> protocol instead of <code class="code">cat</code> or
|
||
<code class="code">copy</code> which will avoid creation of a potentially huge intermediate file.
|
||
</p>
|
||
<div class="example">
|
||
<pre class="example-preformatted">ffmpeg -i input1.avi -qscale:v 1 intermediate1.mpg
|
||
ffmpeg -i input2.avi -qscale:v 1 intermediate2.mpg
|
||
ffmpeg -i concat:"intermediate1.mpg|intermediate2.mpg" -c copy intermediate_all.mpg
|
||
ffmpeg -i intermediate_all.mpg -qscale:v 2 output.avi
|
||
</pre></div>
|
||
|
||
<p>Note that you may need to escape the character "|" which is special for many
|
||
shells.
|
||
</p>
|
||
<p>Another option is usage of named pipes, should your platform support it:
|
||
</p>
|
||
<div class="example">
|
||
<pre class="example-preformatted">mkfifo intermediate1.mpg
|
||
mkfifo intermediate2.mpg
|
||
ffmpeg -i input1.avi -qscale:v 1 -y intermediate1.mpg < /dev/null &
|
||
ffmpeg -i input2.avi -qscale:v 1 -y intermediate2.mpg < /dev/null &
|
||
cat intermediate1.mpg intermediate2.mpg |\
|
||
ffmpeg -f mpeg -i - -c:v mpeg4 -c:a libmp3lame output.avi
|
||
</pre></div>
|
||
|
||
</div>
|
||
<div class="subsection-level-extent" id="Concatenating-using-raw-audio-and-video">
|
||
<h4 class="subsection">3.14.4 Concatenating using raw audio and video</h4>
|
||
|
||
<p>Similarly, the yuv4mpegpipe format, and the raw video, raw audio codecs also
|
||
allow concatenation, and the transcoding step is almost lossless.
|
||
When using multiple yuv4mpegpipe(s), the first line needs to be discarded
|
||
from all but the first stream. This can be accomplished by piping through
|
||
<code class="code">tail</code> as seen below. Note that when piping through <code class="code">tail</code> you
|
||
must use command grouping, <code class="code">{ ;}</code>, to background properly.
|
||
</p>
|
||
<p>For example, let’s say we want to concatenate two FLV files into an
|
||
output.flv file:
|
||
</p>
|
||
<div class="example">
|
||
<pre class="example-preformatted">mkfifo temp1.a
|
||
mkfifo temp1.v
|
||
mkfifo temp2.a
|
||
mkfifo temp2.v
|
||
mkfifo all.a
|
||
mkfifo all.v
|
||
ffmpeg -i input1.flv -vn -f u16le -c:a pcm_s16le -ac 2 -ar 44100 - > temp1.a < /dev/null &
|
||
ffmpeg -i input2.flv -vn -f u16le -c:a pcm_s16le -ac 2 -ar 44100 - > temp2.a < /dev/null &
|
||
ffmpeg -i input1.flv -an -f yuv4mpegpipe - > temp1.v < /dev/null &
|
||
{ ffmpeg -i input2.flv -an -f yuv4mpegpipe - < /dev/null | tail -n +2 > temp2.v ; } &
|
||
cat temp1.a temp2.a > all.a &
|
||
cat temp1.v temp2.v > all.v &
|
||
ffmpeg -f u16le -c:a pcm_s16le -ac 2 -ar 44100 -i all.a \
|
||
-f yuv4mpegpipe -i all.v \
|
||
-y output.flv
|
||
rm temp[12].[av] all.[av]
|
||
</pre></div>
|
||
|
||
</div>
|
||
</div>
|
||
<div class="section-level-extent" id="Using-_002df-lavfi_002c-audio-becomes-mono-for-no-apparent-reason_002e">
|
||
<h3 class="section">3.15 Using <samp class="option">-f lavfi</samp>, audio becomes mono for no apparent reason.</h3>
|
||
|
||
<p>Use <samp class="option">-dumpgraph -</samp> to find out exactly where the channel layout is
|
||
lost.
|
||
</p>
|
||
<p>Most likely, it is through <code class="code">auto-inserted aresample</code>. Try to understand
|
||
why the converting filter was needed at that place.
|
||
</p>
|
||
<p>Just before the output is a likely place, as <samp class="option">-f lavfi</samp> currently
|
||
only support packed S16.
|
||
</p>
|
||
<p>Then insert the correct <code class="code">aformat</code> explicitly in the filtergraph,
|
||
specifying the exact format.
|
||
</p>
|
||
<div class="example">
|
||
<pre class="example-preformatted">aformat=sample_fmts=s16:channel_layouts=stereo
|
||
</pre></div>
|
||
|
||
</div>
|
||
<div class="section-level-extent" id="Why-does-FFmpeg-not-see-the-subtitles-in-my-VOB-file_003f">
|
||
<h3 class="section">3.16 Why does FFmpeg not see the subtitles in my VOB file?</h3>
|
||
|
||
<p>VOB and a few other formats do not have a global header that describes
|
||
everything present in the file. Instead, applications are supposed to scan
|
||
the file to see what it contains. Since VOB files are frequently large, only
|
||
the beginning is scanned. If the subtitles happen only later in the file,
|
||
they will not be initially detected.
|
||
</p>
|
||
<p>Some applications, including the <code class="code">ffmpeg</code> command-line tool, can only
|
||
work with streams that were detected during the initial scan; streams that
|
||
are detected later are ignored.
|
||
</p>
|
||
<p>The size of the initial scan is controlled by two options: <code class="code">probesize</code>
|
||
(default ~5 Mo) and <code class="code">analyzeduration</code> (default 5,000,000 µs = 5 s). For
|
||
the subtitle stream to be detected, both values must be large enough.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="Why-was-the-ffmpeg-_002dsameq-option-removed_003f-What-to-use-instead_003f">
|
||
<h3 class="section">3.17 Why was the <code class="command">ffmpeg</code> <samp class="option">-sameq</samp> option removed? What to use instead?</h3>
|
||
|
||
<p>The <samp class="option">-sameq</samp> option meant "same quantizer", and made sense only in a
|
||
very limited set of cases. Unfortunately, a lot of people mistook it for
|
||
"same quality" and used it in places where it did not make sense: it had
|
||
roughly the expected visible effect, but achieved it in a very inefficient
|
||
way.
|
||
</p>
|
||
<p>Each encoder has its own set of options to set the quality-vs-size balance,
|
||
use the options for the encoder you are using to set the quality level to a
|
||
point acceptable for your tastes. The most common options to do that are
|
||
<samp class="option">-qscale</samp> and <samp class="option">-qmax</samp>, but you should peruse the documentation
|
||
of the encoder you chose.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="I-have-a-stretched-video_002c-why-does-scaling-does-not-fix-it_003f">
|
||
<h3 class="section">3.18 I have a stretched video, why does scaling does not fix it?</h3>
|
||
|
||
<p>A lot of video codecs and formats can store the <em class="emph">aspect ratio</em> of the
|
||
video: this is the ratio between the width and the height of either the full
|
||
image (DAR, display aspect ratio) or individual pixels (SAR, sample aspect
|
||
ratio). For example, EGA screens at resolution 640×350 had 4:3 DAR and 35:48
|
||
SAR.
|
||
</p>
|
||
<p>Most still image processing work with square pixels, i.e. 1:1 SAR, but a lot
|
||
of video standards, especially from the analogic-numeric transition era, use
|
||
non-square pixels.
|
||
</p>
|
||
<p>Most processing filters in FFmpeg handle the aspect ratio to avoid
|
||
stretching the image: cropping adjusts the DAR to keep the SAR constant,
|
||
scaling adjusts the SAR to keep the DAR constant.
|
||
</p>
|
||
<p>If you want to stretch, or “unstretch”, the image, you need to override the
|
||
information with the
|
||
<a class="url" href="ffmpeg-filters.html#setdar_002c-setsar"><code class="code">setdar or setsar filters</code></a>.
|
||
</p>
|
||
<p>Do not forget to examine carefully the original video to check whether the
|
||
stretching comes from the image or from the aspect ratio information.
|
||
</p>
|
||
<p>For example, to fix a badly encoded EGA capture, use the following commands,
|
||
either the first one to upscale to square pixels or the second one to set
|
||
the correct aspect ratio or the third one to avoid transcoding (may not work
|
||
depending on the format / codec / player / phase of the moon):
|
||
</p>
|
||
<div class="example">
|
||
<pre class="example-preformatted">ffmpeg -i ega_screen.nut -vf scale=640:480,setsar=1 ega_screen_scaled.nut
|
||
ffmpeg -i ega_screen.nut -vf setdar=4/3 ega_screen_anamorphic.nut
|
||
ffmpeg -i ega_screen.nut -aspect 4/3 -c copy ega_screen_overridden.nut
|
||
</pre></div>
|
||
|
||
<a class="anchor" id="background-task"></a></div>
|
||
<div class="section-level-extent" id="How-do-I-run-ffmpeg-as-a-background-task_003f">
|
||
<h3 class="section">3.19 How do I run ffmpeg as a background task?</h3>
|
||
|
||
<p>ffmpeg normally checks the console input, for entries like "q" to stop
|
||
and "?" to give help, while performing operations. ffmpeg does not have a way of
|
||
detecting when it is running as a background task.
|
||
When it checks the console input, that can cause the process running ffmpeg
|
||
in the background to suspend.
|
||
</p>
|
||
<p>To prevent those input checks, allowing ffmpeg to run as a background task,
|
||
use the <a class="url" href="ffmpeg.html#stdin-option"><code class="code">-nostdin</code> option</a>
|
||
in the ffmpeg invocation. This is effective whether you run ffmpeg in a shell
|
||
or invoke ffmpeg in its own process via an operating system API.
|
||
</p>
|
||
<p>As an alternative, when you are running ffmpeg in a shell, you can redirect
|
||
standard input to <code class="code">/dev/null</code> (on Linux and macOS)
|
||
or <code class="code">NUL</code> (on Windows). You can do this redirect either
|
||
on the ffmpeg invocation, or from a shell script which calls ffmpeg.
|
||
</p>
|
||
<p>For example:
|
||
</p>
|
||
<div class="example">
|
||
<pre class="example-preformatted">ffmpeg -nostdin -i INPUT OUTPUT
|
||
</pre></div>
|
||
|
||
<p>or (on Linux, macOS, and other UNIX-like shells):
|
||
</p>
|
||
<div class="example">
|
||
<pre class="example-preformatted">ffmpeg -i INPUT OUTPUT </dev/null
|
||
</pre></div>
|
||
|
||
<p>or (on Windows):
|
||
</p>
|
||
<div class="example">
|
||
<pre class="example-preformatted">ffmpeg -i INPUT OUTPUT <NUL
|
||
</pre></div>
|
||
|
||
</div>
|
||
<div class="section-level-extent" id="How-do-I-prevent-ffmpeg-from-suspending-with-a-message-like-suspended-_0028tty-output_0029_003f">
|
||
<h3 class="section">3.20 How do I prevent ffmpeg from suspending with a message like <em class="emph">suspended (tty output)</em>?</h3>
|
||
|
||
<p>If you run ffmpeg in the background, you may find that its process suspends.
|
||
There may be a message like <em class="emph">suspended (tty output)</em>. The question is how
|
||
to prevent the process from being suspended.
|
||
</p>
|
||
<p>For example:
|
||
</p>
|
||
<div class="example">
|
||
<pre class="example-preformatted">% ffmpeg -i INPUT OUTPUT &> ~/tmp/log.txt &
|
||
[1] 93352
|
||
%
|
||
[1] + suspended (tty output) ffmpeg -i INPUT OUTPUT &>
|
||
</pre></div>
|
||
|
||
<p>The message "tty output" notwithstanding, the problem here is that
|
||
ffmpeg normally checks the console input when it runs. The operating system
|
||
detects this, and suspends the process until you can bring it to the
|
||
foreground and attend to it.
|
||
</p>
|
||
<p>The solution is to use the right techniques to tell ffmpeg not to consult
|
||
console input. You can use the
|
||
<a class="url" href="ffmpeg.html#stdin-option"><code class="code">-nostdin</code> option</a>,
|
||
or redirect standard input with <code class="code">< /dev/null</code>.
|
||
See FAQ
|
||
<a class="ref" href="#background-task"><em class="emph">How do I run ffmpeg as a background task?</em></a>
|
||
for details.
|
||
</p>
|
||
</div>
|
||
</div>
|
||
<div class="chapter-level-extent" id="Development">
|
||
<h2 class="chapter">4 Development</h2>
|
||
|
||
<ul class="mini-toc">
|
||
<li><a href="#Are-there-examples-illustrating-how-to-use-the-FFmpeg-libraries_002c-particularly-libavcodec-and-libavformat_003f" accesskey="1">Are there examples illustrating how to use the FFmpeg libraries, particularly libavcodec and libavformat?</a></li>
|
||
<li><a href="#Can-you-support-my-C-compiler-XXX_003f" accesskey="2">Can you support my C compiler XXX?</a></li>
|
||
<li><a href="#Is-Microsoft-Visual-C_002b_002b-supported_003f" accesskey="3">Is Microsoft Visual C++ supported?</a></li>
|
||
<li><a href="#Can-you-add-automake_002c-libtool-or-autoconf-support_003f" accesskey="4">Can you add automake, libtool or autoconf support?</a></li>
|
||
<li><a href="#Why-not-rewrite-FFmpeg-in-object_002doriented-C_002b_002b_003f" accesskey="5">Why not rewrite FFmpeg in object-oriented C++?</a></li>
|
||
<li><a href="#Why-are-the-ffmpeg-programs-devoid-of-debugging-symbols_003f" accesskey="6">Why are the ffmpeg programs devoid of debugging symbols?</a></li>
|
||
<li><a href="#I-do-not-like-the-LGPL_002c-can-I-contribute-code-under-the-GPL-instead_003f" accesskey="7">I do not like the LGPL, can I contribute code under the GPL instead?</a></li>
|
||
<li><a href="#I_0027m-using-FFmpeg-from-within-my-C-application-but-the-linker-complains-about-missing-symbols-from-the-libraries-themselves_002e" accesskey="8">I’m using FFmpeg from within my C application but the linker complains about missing symbols from the libraries themselves.</a></li>
|
||
<li><a href="#I_0027m-using-FFmpeg-from-within-my-C_002b_002b-application-but-the-linker-complains-about-missing-symbols-which-seem-to-be-available_002e" accesskey="9">I’m using FFmpeg from within my C++ application but the linker complains about missing symbols which seem to be available.</a></li>
|
||
<li><a href="#I_0027m-using-libavutil-from-within-my-C_002b_002b-application-but-the-compiler-complains-about-_0027UINT64_005fC_0027-was-not-declared-in-this-scope">I’m using libavutil from within my C++ application but the compiler complains about ’UINT64_C’ was not declared in this scope</a></li>
|
||
<li><a href="#I-have-a-file-in-memory-_002f-a-API-different-from-_002aopen_002f_002aread_002f-libc-how-do-I-use-it-with-libavformat_003f">I have a file in memory / a API different from *open/*read/ libc how do I use it with libavformat?</a></li>
|
||
<li><a href="#Where-is-the-documentation-about-ffv1_002c-msmpeg4_002c-asv1_002c-4xm_003f">Where is the documentation about ffv1, msmpeg4, asv1, 4xm?</a></li>
|
||
<li><a href="#How-do-I-feed-H_002e263_002dRTP-_0028and-other-codecs-in-RTP_0029-to-libavcodec_003f">How do I feed H.263-RTP (and other codecs in RTP) to libavcodec?</a></li>
|
||
<li><a href="#AVStream_002er_005fframe_005frate-is-wrong_002c-it-is-much-larger-than-the-frame-rate_002e">AVStream.r_frame_rate is wrong, it is much larger than the frame rate.</a></li>
|
||
<li><a href="#Why-is-make-fate-not-running-all-tests_003f">Why is <code class="code">make fate</code> not running all tests?</a></li>
|
||
<li><a href="#Why-is-make-fate-not-finding-the-samples_003f">Why is <code class="code">make fate</code> not finding the samples?</a></li>
|
||
</ul>
|
||
<div class="section-level-extent" id="Are-there-examples-illustrating-how-to-use-the-FFmpeg-libraries_002c-particularly-libavcodec-and-libavformat_003f">
|
||
<h3 class="section">4.1 Are there examples illustrating how to use the FFmpeg libraries, particularly libavcodec and libavformat?</h3>
|
||
|
||
<p>Yes. Check the <samp class="file">doc/examples</samp> directory in the source
|
||
repository, also available online at:
|
||
<a class="url" href="https://github.com/FFmpeg/FFmpeg/tree/master/doc/examples">https://github.com/FFmpeg/FFmpeg/tree/master/doc/examples</a>.
|
||
</p>
|
||
<p>Examples are also installed by default, usually in
|
||
<code class="code">$PREFIX/share/ffmpeg/examples</code>.
|
||
</p>
|
||
<p>Also you may read the Developers Guide of the FFmpeg documentation. Alternatively,
|
||
examine the source code for one of the many open source projects that
|
||
already incorporate FFmpeg at (<a class="url" href="projects.html">projects.html</a>).
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="Can-you-support-my-C-compiler-XXX_003f">
|
||
<h3 class="section">4.2 Can you support my C compiler XXX?</h3>
|
||
|
||
<p>It depends. If your compiler is C99-compliant, then patches to support
|
||
it are likely to be welcome if they do not pollute the source code
|
||
with <code class="code">#ifdef</code>s related to the compiler.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="Is-Microsoft-Visual-C_002b_002b-supported_003f">
|
||
<h3 class="section">4.3 Is Microsoft Visual C++ supported?</h3>
|
||
|
||
<p>Yes. Please see the <a class="uref" href="platform.html">Microsoft Visual C++</a>
|
||
section in the FFmpeg documentation.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="Can-you-add-automake_002c-libtool-or-autoconf-support_003f">
|
||
<h3 class="section">4.4 Can you add automake, libtool or autoconf support?</h3>
|
||
|
||
<p>No. These tools are too bloated and they complicate the build.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="Why-not-rewrite-FFmpeg-in-object_002doriented-C_002b_002b_003f">
|
||
<h3 class="section">4.5 Why not rewrite FFmpeg in object-oriented C++?</h3>
|
||
|
||
<p>FFmpeg is already organized in a highly modular manner and does not need to
|
||
be rewritten in a formal object language. Further, many of the developers
|
||
favor straight C; it works for them. For more arguments on this matter,
|
||
read <a class="uref" href="https://web.archive.org/web/20111004021423/http://kernel.org/pub/linux/docs/lkml/#s15">"Programming Religion"</a>.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="Why-are-the-ffmpeg-programs-devoid-of-debugging-symbols_003f">
|
||
<h3 class="section">4.6 Why are the ffmpeg programs devoid of debugging symbols?</h3>
|
||
|
||
<p>The build process creates <code class="command">ffmpeg_g</code>, <code class="command">ffplay_g</code>, etc. which
|
||
contain full debug information. Those binaries are stripped to create
|
||
<code class="command">ffmpeg</code>, <code class="command">ffplay</code>, etc. If you need the debug information, use
|
||
the *_g versions.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="I-do-not-like-the-LGPL_002c-can-I-contribute-code-under-the-GPL-instead_003f">
|
||
<h3 class="section">4.7 I do not like the LGPL, can I contribute code under the GPL instead?</h3>
|
||
|
||
<p>Yes, as long as the code is optional and can easily and cleanly be placed
|
||
under #if CONFIG_GPL without breaking anything. So, for example, a new codec
|
||
or filter would be OK under GPL while a bug fix to LGPL code would not.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="I_0027m-using-FFmpeg-from-within-my-C-application-but-the-linker-complains-about-missing-symbols-from-the-libraries-themselves_002e">
|
||
<h3 class="section">4.8 I’m using FFmpeg from within my C application but the linker complains about missing symbols from the libraries themselves.</h3>
|
||
|
||
<p>FFmpeg builds static libraries by default. In static libraries, dependencies
|
||
are not handled. That has two consequences. First, you must specify the
|
||
libraries in dependency order: <code class="code">-lavdevice</code> must come before
|
||
<code class="code">-lavformat</code>, <code class="code">-lavutil</code> must come after everything else, etc.
|
||
Second, external libraries that are used in FFmpeg have to be specified too.
|
||
</p>
|
||
<p>An easy way to get the full list of required libraries in dependency order
|
||
is to use <code class="code">pkg-config</code>.
|
||
</p>
|
||
<div class="example">
|
||
<pre class="example-preformatted">c99 -o program program.c $(pkg-config --cflags --libs libavformat libavcodec)
|
||
</pre></div>
|
||
|
||
<p>See <samp class="file">doc/example/Makefile</samp> and <samp class="file">doc/example/pc-uninstalled</samp> for
|
||
more details.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="I_0027m-using-FFmpeg-from-within-my-C_002b_002b-application-but-the-linker-complains-about-missing-symbols-which-seem-to-be-available_002e">
|
||
<h3 class="section">4.9 I’m using FFmpeg from within my C++ application but the linker complains about missing symbols which seem to be available.</h3>
|
||
|
||
<p>FFmpeg is a pure C project, so to use the libraries within your C++ application
|
||
you need to explicitly state that you are using a C library. You can do this by
|
||
encompassing your FFmpeg includes using <code class="code">extern "C"</code>.
|
||
</p>
|
||
<p>See <a class="url" href="http://www.parashift.com/c++-faq-lite/mixing-c-and-cpp.html#faq-32.3">http://www.parashift.com/c++-faq-lite/mixing-c-and-cpp.html#faq-32.3</a>
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="I_0027m-using-libavutil-from-within-my-C_002b_002b-application-but-the-compiler-complains-about-_0027UINT64_005fC_0027-was-not-declared-in-this-scope">
|
||
<h3 class="section">4.10 I’m using libavutil from within my C++ application but the compiler complains about ’UINT64_C’ was not declared in this scope</h3>
|
||
|
||
<p>FFmpeg is a pure C project using C99 math features, in order to enable C++
|
||
to use them you have to append -D__STDC_CONSTANT_MACROS to your CXXFLAGS
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="I-have-a-file-in-memory-_002f-a-API-different-from-_002aopen_002f_002aread_002f-libc-how-do-I-use-it-with-libavformat_003f">
|
||
<h3 class="section">4.11 I have a file in memory / a API different from *open/*read/ libc how do I use it with libavformat?</h3>
|
||
|
||
<p>You have to create a custom AVIOContext using <code class="code">avio_alloc_context</code>,
|
||
see <samp class="file">libavformat/aviobuf.c</samp> in FFmpeg and <samp class="file">libmpdemux/demux_lavf.c</samp> in MPlayer or MPlayer2 sources.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="Where-is-the-documentation-about-ffv1_002c-msmpeg4_002c-asv1_002c-4xm_003f">
|
||
<h3 class="section">4.12 Where is the documentation about ffv1, msmpeg4, asv1, 4xm?</h3>
|
||
|
||
<p>see <a class="url" href="https://www.ffmpeg.org/~michael/">https://www.ffmpeg.org/~michael/</a>
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="How-do-I-feed-H_002e263_002dRTP-_0028and-other-codecs-in-RTP_0029-to-libavcodec_003f">
|
||
<h3 class="section">4.13 How do I feed H.263-RTP (and other codecs in RTP) to libavcodec?</h3>
|
||
|
||
<p>Even if peculiar since it is network oriented, RTP is a container like any
|
||
other. You have to <em class="emph">demux</em> RTP before feeding the payload to libavcodec.
|
||
In this specific case please look at RFC 4629 to see how it should be done.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="AVStream_002er_005fframe_005frate-is-wrong_002c-it-is-much-larger-than-the-frame-rate_002e">
|
||
<h3 class="section">4.14 AVStream.r_frame_rate is wrong, it is much larger than the frame rate.</h3>
|
||
|
||
<p><code class="code">r_frame_rate</code> is NOT the average frame rate, it is the smallest frame rate
|
||
that can accurately represent all timestamps. So no, it is not
|
||
wrong if it is larger than the average!
|
||
For example, if you have mixed 25 and 30 fps content, then <code class="code">r_frame_rate</code>
|
||
will be 150 (it is the least common multiple).
|
||
If you are looking for the average frame rate, see <code class="code">AVStream.avg_frame_rate</code>.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="Why-is-make-fate-not-running-all-tests_003f">
|
||
<h3 class="section">4.15 Why is <code class="code">make fate</code> not running all tests?</h3>
|
||
|
||
<p>Make sure you have the fate-suite samples and the <code class="code">SAMPLES</code> Make variable
|
||
or <code class="code">FATE_SAMPLES</code> environment variable or the <code class="code">--samples</code>
|
||
<code class="command">configure</code> option is set to the right path.
|
||
</p>
|
||
</div>
|
||
<div class="section-level-extent" id="Why-is-make-fate-not-finding-the-samples_003f">
|
||
<h3 class="section">4.16 Why is <code class="code">make fate</code> not finding the samples?</h3>
|
||
|
||
<p>Do you happen to have a <code class="code">~</code> character in the samples path to indicate a
|
||
home directory? The value is used in ways where the shell cannot expand it,
|
||
causing FATE to not find files. Just replace <code class="code">~</code> by the full path.
|
||
</p>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
|
||
|
||
|
||
</body>
|
||
</html>
|